Braking mechanism



Jan. 17, 1928. 1,656,174

A. C. DAHL BRAKING MECHANI SM Filed June 3o, 192g Patented Jan. 17, 1928.'

UNITED STATES PATENT OFFICE.

i ARTHUR CLARENCE DAHI., or IIINSDALE, ILLINOIS, AssIGNOR To WESTERN ELEC; TRIC COMPANY, INCORPORATED, OF NRW YORK, N. Y., A 'CORPORATION or NRW YGRK.

Application led .Tune 30, 1926. Serial No. 119,523.

l This invention relatesto braking mechanisms7 and more particularly to an electromagnetic. brake foi-.motor driven apparatus. ln the operation of apparatus driven by l? electrical motors it is not only desirable but often important that the apparatus be stopped as quickly as possible upon discontinuing the supply of current to the motor. One

- instanceof this nature occurs in the Operation of high speed motor driven woodworking saws which are necessarily stopped quite frequent-ly to change or examine nthe saw blades. In such instances, unless some means is provided forstopping the motor when the supply circuit is opened, it is obvious that an appreciable amount of time may be lost waiting for the apparatus to to come to a full stop. Furthermore, due to the unavoidable noises that are present in rooms or factories where apparatus of this type are usually operated, it is sometimes very difficult for the operator to ascertain when the motor or saw is at rest without approaching dangerously near the sawY blade.

The principal object of the present invention is to provide an improved and simplified mechanism for quickly and effectively stopping the operation of motor driven ap- 3@ paratus when the motor operating power is discontinued.

In accordance with the general features of the invention there is provided in one embodiment thereof a spring actuated friction .35 brake member adapted to normally hold the motor shaft stationary. Electromagnetic means is included in the motor -supply circuit for releasing the friction brake member when the supply circuit is closed.

Other features and advantages of the invention will become apparent in the following detail description, reference being had to the accompanying drawing, wherein Fig. 1 is a plan view ofa motor driven saw embodying the features of the invention, a portion of the supporting frame being omitted to more clearly illustrate .the invention;

Fi 2 is an enlarged detail section of the bra-king mechanism shown in Fi'g. 1, and

Fig. 3 isv a diagram of an electrical circuit suitable for operating the apparatus shown in `Fig. 1.

u As shown in the drawing, the numeral 10 indlcates 21.-supporting frame for a bench or table (not shown) of a motor driven saw 11. In' the present embodiment of the invention, the saw 11 is rigidly secured at one end of an armature shaft 12 of an electric motor 13. kThe opposite end of the shaft 12 terminatesfin a casing 15 which houses the improved braking mechanism. rlhe casing 15 is secured to one lside of the frame 10 and is provided with a removable head 16 which is secured to the casing proper by means of bolts 17. p

Secured to the end of the shaft 12 is a collar7 20 to which is slidably keyeda friction disk 21 having annular friction pads 22 and 23 secured on opposite sides thereof. The friction pad 22 is positioned to engage a wall 24 of an annular recess 25 formed in the casing 15. A compression spring 27 encircling an elongated hub 28 of the friction disk 21 and interposed between the latter and a side wall 29 of the casing serves to normally disengage the friction pad 22 from the wall 24, as clearly shown in Fig. 2.

Rotatably and slidably supported in the removable head 16 and positioned in axial alignment with the shaft 12 is a stud shaft 30 upon which is loosely mounted a cupshaped member 31 having an annular surface 32 designed to engage the friction pad 23. Disposed within an annular recess 34 formed in the head 16 is a compression spring 35 which is relatively stronger than the spring 27. As shown in Fig. 2, the spring 35 encircles the stud shaft 30 and is disposed between "the member 31 and the endwall of the recess 311. It is thereforel obvious thatthe spring 35 normally urges the member 31 towards the friction disk 21.

One end ofthe stud shaft 30 protrudes through the head 16 of the casing and has secured thereto a collar 38. Pivoted at 39 to the head 16 is a lever 40 which is bifurcated at one end to st-raddle the outwardly projecting portion of the shaft 30. The Opposite end of the lever 40 is operatively connected to a plunger L12 of an electromagnetic solenoid 43 by means of an adjustable link 44 (Fig. 1). v The solenoid 43 is secured to one side'of the frame 10 and is connected in the motor supply circuit in such manner that it is energized when the supplycircuit for controlling the brake actu' pivot 39. When energized, the solenoid 43.

overcomes the action of the springl 35 and the cup-shaped member 31 is thereby disen" ugaged from the friction pad 23. Due to the action of the spring 27, the friction padv22 is also disengaged from the wall 24 ofthe casing, thereby completel releasing the braking mechanism. It s ould be' understood that this action takes place immedi ately upon closing the motor supply circuit to start the operation of the apparatus.

When the motor supply circuit is opened, 4

the solenoid 43 is tie-energized, and due to the action of the spring 35 the cup-shaped member 31 is engaged with the friction pad 23. Also, since the spring 35 is stronger than the spring 27, the friction disk 21 is shifted to the left, slightly, causing the engagement of the friction pad 22 with the wall 24 of' the casing. In this lway the motor shaft 12 is immediately subjected to averyl effective brake which causesthe motor'to stop after a very fewfrevolutions.-

Although the invention is herein illustrated and described in connection with'a motor driven saw, it should be understood that the novel features thereof are capable of lother applications and that the invention should be limited only by the'scope of the appended claims. d `What is claimds:

ber slidable on and rotatable with said shaft, said brake member having friction pads at1ng` member.

2. In'a motordrive'n apparatus', ait elec' trical supplycir-cult including al motor, av

shaft driven thereby, a friction brake meinber slidable on and rotatable with said shaft;

a coil spring concentricl with said 'shaft' for normally rendering said brake member ineffective, a second spring opposing the first s ring for renderin -the brake member e ective, and means. included in I and controlled by the. supply circuit for rendering the lsecond spring ineffective when .the supply circuit is closed. w

l 3. Ina motor' driven ap aratus, an electrical. supply circuit inclu' ig ra, autor, a.

circuit is closed.

` the lsupp p cooperating with said solenoid 1.- In a motor driven apparatus, an elec-'1v trical supply circuit including a motoria shaft driven thereby, a friction brake memshaft driven thereby, a friction brakemember slidable on and rotatable with said shaft,

said brake member having friction' ads sei cured on opposite sides thereof, a coi spring concentric with the power shaft normally rendering said brake\ member ineffective, a

spring pressed member for rendering the brake member effective, and electromagnetic means includedv in and controlled by the supply circuit for rendering the spring pressed member ineffective when the supply 4. In a motor driven ap Iaratus, anelectrical supply circuit inclu ing a motor, a shaft driven thereby, a friction brake member slidable on and rotatable with said'shaft,

said brake member having frictionpads secured on opposite sides thereof, a spring pressed -member normally rendering said brake member effective, a pivoted arm operatively connected to said member, and means operatively connected to said arm and controlled by the. supply circuit yfor rendering the spring pressed member ineffective.

5. In a motor driven apparatus, an electrical supply circuit including a motor, a"

shaft driven thereby,.said shaft terminating in a stationary housing, a friction' brake member slidable thereon and rotatable with said shaft, said brake member having annular friction pads secured on opposite sides thereof, a spring pressed 4member normally 1 engaging oneof said pads and causing the engagement of the other pad with a portion of the housing to render the brake member effective, a solenoid included in and controlled by the supply circuit for rendering the spring pressed member ineffective when y circuit is closed, and aspring for rendering the brake member ineffective.V Y

6. In a motor driven apparatus, an electrical supply circuit including a motor, a

shaft driven tlereby, said shaft terminating 1n a stationary housing, a friction brake Vmember having friction pads secured on ops` posite sides thereof, a coil spring concentric with the power shaft normally rendering the brake member ineffective, an annular non-rotatable friction member having aface adjacent one 'of the friction pads, a coil sprlng for 'engaging said ymember with one of the friction pads and causing the engagelment of the other pad with fa portion of the housing, a pivoted'a'rm operatively connected to the said annular non-rotatable vfriction member, and means operativelyjconnected'to said arm and controlled by the electrical supply circuit for rendering the spring pressed member ineffective. f

In witness whereof, I hereunto subscribe my name this 18th day of June, A. D. 1926.`

Amana cLARENca DAHL. 

